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Polyoxometalates (POMs) are nanosized molecular metal oxide anion clusters with tuneable structures and functionalities, and they exhibit a redox chemistry and catalytic activity in multielectron redox processes. These are typically poor electrical conductors (<10−10 Scm−1), which is attributed to negligible electronic interactions among anions in the solid state. Since the reduced electrons on the d0 metals in POMs are delocalized, electrical conductivity was improved when judicious pathways for the electrons were created by bridging the POMs. Utilized with the electronic interactions between bridging oxygen atoms with the highest occupied molecular orbital in the POMs and the metal dz2 orbitals in the multinuclear platinum complexes, and three mixed‐valent assemblies were synthesized and characterized. Simply mixing Keggin‐type or Dawson‐type POMs with tetranuclear or trinuclear platinum complexes in solution afforded three single crystals, and all three compounds were paramagnetic with mixed oxidation states and better conductivities at room temperature than the parent compounds. [ABSTRACT FROM AUTHOR]

Two types of isostructural iron-cobalt/nickel-antimony-oxo tartrate cluster-based compounds, namely (H3O)(Me2NH2)[M(H2O)6]2[FeII2SbIII12(μ4-O)3(μ3-O)8(tta)6]·6H2O (M = Co (1); Ni (3)), H5/3[Co2.5FeII4/3FeIII3(H2O)13SbV1/3FeIII2/3(μ4-O)2(μ3-O)4SbIII6(μ3-O)2(tta)6]·2H2O (2) and H2[Ni2.25FeII1.5FeIII3(H2O)14SbV0.25FeIII0.75(μ4-O)2(μ3-O)4SbIII6(μ3-O)2(tta)6]·2H2O (4) (H4tta = tartaric acid) were synthesized via simple solvothermal reactions. All the clusters in the structures adopt sandwich configurations, that is, bilayer sandwich configuration in 1 and 3 and monolayer sandwich configuration in 2 and 4. Interestingly, the monolayer sandwiched compounds 2 and 4 represent rare examples of cluster-based compounds containing mixed-valence Sb(III, V), whose center of the intermediate layer is the co-occupied [FexSbV1−x]. This is different from that of previously reported sandwich-type antimony-oxo clusters in which the center position is either occupied by a transition metal ion or a Sb(V) alone. Thus, the discovery of title compounds 2 and 4 makes the evolution of center metal ion more complete, that is, from M, MxSbV1−x to SbV. All the title compounds were fully characterized, and the photocatalysis, proton conduction and magnetism of compounds 2 and 4 were studied. [ABSTRACT FROM AUTHOR]

One electron oxidation of the monometallic alkenylacetylide complexes [Ru{C≡CC(R)=CH2}(dppe)Cp*] (1) and [Ru{C≡CC(R)=CH2}Cl(dppe)2] (2) (R = Ph (a); R = 4-MeS-C6H4 (b)) generates in each case a dinuclear bis(allenylidene) complex [{Ru}2{μ-C=C=C(R)–CH2–H2C–(R)C=C=C}][PF6]2 ({Ru} = Ru(dppe)Cp* ([3a,b][PF6]2); {Ru} = RuCl(dppe)2 ([4a,b][PF6]2), containing an unsaturated ethane bridge between both allenylidene moieties. Deprotonation of this ethane bridge results in the formation of the previously reported octa-3,5-diene-1,7-diyndiyl-bridged bimetallic species [{Ru}2{μ-C≡CC(R)=CH–HC=(R)CC≡C}] ({Ru} = Ru(dppe)Cp* (5a,b); {Ru} = RuCl(dppe)2 (6a,b). The isolation of these complexes illustrates a general synthetic route to these conjugated bimetallic species from monomeric alkenylacetylide precursors. Electrochemical and spectroelectrochemical investigations evince the ready formation of the representative redox series [5a]n+, and TD-DFT calculations performed on optimised structures featuring the simplified {Ru(dmpe)Cp} coordination sphere [{Ru(dmpe)Cp}2{μ-C≡CC(Ph)=HC–CH(Ph)CC≡C}]n+ ([5a†]n+) (n = 0, 1, 2) reveal significant delocalisation of the unpaired charge in the formally mixed-valent species (n = 1), consistent with Class III assignment within the Robin–Day classification scheme. [ABSTRACT FROM AUTHOR]

We report two novel three‐dimensional copper‐benzoquinoid metal–organic frameworks (MOFs), [Cu4L3]n and [Cu4L3 ⋅ Cu(iq)3]n (LH4=1,4‐dicyano‐2,3,5,6‐tetrahydroxybenzene, iq=isoquinoline). Spectroscopic techniques and computational studies reveal the unprecedented mixed valency in MOFs, formal Cu(I)/Cu(III). This is the first time that formally Cu(III) species are witnessed in metal–organic extended solids. The coordination between the mixed‐valence metal and redox‐non‐innocent ligand L, which promotes through‐bond charge transfer between Cu metal sites, allows better metal‐ligand orbital overlap of the d‐π conjugation, leading to strong long‐range delocalization and semiconducting behavior. Our findings highlight the significance of the unique mixed valency between formal Cu(I) and highly‐covalent Cu(III), non‐innocent ligand, and pore environments of these bench stable Cu(III)‐containing frameworks on multielectron transfer and electrochemical properties. [ABSTRACT FROM AUTHOR]

Reaction of nickel and zinc triflates with the tridentate leucoverdazyl 1-isopropyl-3,5-di (2′-pyridyl)-6-oxo-2H-tetrazine (dipyvdH) and triethylamine resulted in the neutral coordination compounds M(dipyvd)2 (M = Ni,Zn). In acetonitrile, both compounds undergo two one electron oxidation processes, Zn (dipyvd)2 at −0.28 V and −0.12 V and Ni(dipyvd)2 at −0.32 V and −0.15 V vs ferrocene/ferricenium. Oxidations are ligand based resulting in an intermediate mixed valence species and a cationic bis(verdazyl) compound respectively. Oxidation of the ligand changes a localized, antiaromatic, non-planar 8π electron anion to a planar, delocalized 7π electron radical. The change in ligand structure results in an increase in the octahedral ligand field splitting from 10,500 cm–1 to ∼13,000 cm–1, suggesting an increase in the pi acceptor character of the ligand. In the mixed valence species, spectroscopic data suggests minimal interaction between ligands mediated by the metal center; i.e., these are class I-II systems in the Robin-Day classification.

Neutral [X−{Ir2}−{Ir2}−X] (X=Cl, Br, SCN, I) and dicationic [L−{Ir2}−{Ir2}−L]2+ (L=MeCN, Me2CO) tetrametallic iridium chains made by connecting two dinuclear {Ir2} units ({Ir2}=[Ir2(μ‐OPy)2(CO)4], OPy=2‐pyridonate) by an iridium–iridium bond are described. The complexes exhibit fractional averaged oxidation states of +1.5 and electronic delocalization along the metallic chain. While the axial ligands do not significantly affect the metal–metal bond lengths, the metallic chain has a significant impact on the iridium–L/X bond distances. The complexes show free rotation around the unsupported iridium‐iridium bond in solution, with a low‐energy transition state for the chloride chain. The absorption spectra of these complexes show characteristic bands at 438–504 nm, which can be fine‐tuned by varying the terminal capping ligands. [ABSTRACT FROM AUTHOR]

Carboxymethylcellulose (CMC) is an efficient alternative to synthetic polymeric analogues for utilization as a green stabilizer and reducing agent in the preparation of unique metal nanoparticles due to its attractive features such as multifunctional reactivity, excellent coordination ability, good shaping ability, low cost, green and renewability, biodegradability and biocompatibility. Herein, a practical and straightforward approach was developed for the fabrication of nanocomposite microspheres (CuI/IIONPs@Al–CMC) composed of CuO nanoparticles with Cu(I/II) mixed-valence and CMC, in which the Cu(I) oxidation state dispersed on the surface of CuI/IIO NPs was in situ generated through partial reduction of hydroxyl groups of CMC without needing any additional reductant in the Al3+ crosslinking process. Their composition and structure were systematically characterized by means of inductively coupled plasma, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG) techniques. The resulting CuI/IIONPs@Al–CMC nanocomposite microspheres with CMC three-dimensional (3D) networks can serve as micro- or nano-reactors towards solvent-free aldehyde–alkyne–amine (A3) coupling reactions under mild conditions. The obvious synergistic effect was observed in the control experiments for the A3-couplings model reaction. The control experiments showed that CuI/IIONPs@Al–CMC nanocomposite microspheres exhibited markedly greater reactivity than native CuIIO NPs counterparts. Also, the introduction of Al3+ could facilitate the activation of the carbonyl groups of aldehydes, thus improving the conversion of aldehydes into desired products. The hot filtration test and recycling experiments confirmed that the catalysis is heterogeneous nature, and the catalysts have thermal stability to be reused up to five successive cycles without losing their activity. Mixed-valence copper oxide nanoparticles (CuI/IIO NPs) encapsulated by Al3+ ions crosslinked carboxymethylcellulose (Al–CMC) have been fabricated successfully, which show markedly synergistic performance in aldehyde–alkyne–amine (A3) coupling reactions. [ABSTRACT FROM AUTHOR]

Realizing dual charge transfer (CT) based on stable organic radicals in one system is a long‐sought goal, however, remains challenging. In this work, a stable mixed‐valence radical crystal is designed via a surfactant‐assisted method, namely TTF‐(TTF+•)2‐RC (where TTF = tetrathiafulvalene), containing dual CT interactions. The solubilization of surfactants enables successful co‐crystallization of mixed‐valence TTF molecules with different polarity in aqueous solutions. Short intermolecular distances between adjacent TTF moieties within TTF‐(TTF+•)2‐RC facilitate both inter‐valence CT (IVCT) between neutral TTF and TTF+•, and inter‐radical CT (IRCT) between two TTF+• in radical π‐dimer, which are confirmed by single‐crystal X‐ray diffraction, solid‐state absorption, electron spin resonance measurements, and DFT calculations. Moreover, TTF‐(TTF+•)2‐RC reveals an open‐shell singlet diradical ground state with the antiferromagnetic coupling of 2J = −657 cm−1 and an unprecedented temperature‐dependent magnetic property, manifesting the main monoradical characters of IVCT at 113–203 K while the spin‐spin interactions in radical dimers of IRCT are predominant at 263–353 K. Notably, dual CT characters endow TTF‐(TTF+•)2‐RC with strong light absorption over the full solar spectrum and outstanding stability. As a result, TTF‐(TTF+•)2‐RC exhibits significantly enhanced photothermal property, an increase of 46.6 °C within 180 s upon one‐sun illumination. [ABSTRACT FROM AUTHOR]

The water oxidation reaction is one of the crucial process involves 4e- and 4H+ transfer, which causes a high energy barrier and makes the water-splitting process a slow kinetic reaction. Herein, we have systematically observed the water oxidation activity of La 1-x Ca x MnO 3 (0≤ x ≤ 1) solid solutions by tuning the valence of Mn ion through selective substitution of La3+ with Ca2+. With increasing Ca concentration in La 1-x Ca x MnO 3 solid solutions, the water oxidation activity increases up to x = 0.5 and then decreases. Mixed-valence of Mn generated due to substitution of La3+ with Ca2+, which leads to the double exchange mechanism. This could results in high electrical conduction and a faster electron transfer rate because of the rapid charge exchange between Mn3+ and Mn4+ ions, which pinpoints the reason behind the enhanced oxygen evolution activity. Our findings will be a promising way to relate the Mn mixed-valence with its catalytic activity to design and development of efficient water oxidation catalysts. [Display omitted] • La 1-x Ca x MnO 3 (0 ≤ x ≤ 1) solid solutions were synthesized by citrate-gel method. • Oxidation state of Mn has been tuned between +3 and + 4 in the solid solutions. • Ratio between Mn3+ and Mn4+ plays a crucial role on the water oxidation activity. • La 0.5 Ca 0.5 MnO 3 shows lowest overpotential (570 mV), Tafel slope (173 mV/dec). • La 0.5 Ca 0.5 MnO 3 shows highest photochemical water oxidation TOF (3.57 × 10-3 s−1). [ABSTRACT FROM AUTHOR]

To investigate the effect of ligand remote (>10 Å) substituents on the bridging metal center on the metal‐to‐metal charge transfer (MMCT) properties in cyanidometa‐bridged complexes, a series of new cyanidometal‐bridged complexes and their one‐electron and two‐electron oxidation products have been synthesized and well characterized (namely, trans‐[Cp(dppe)Fe−NC−(L)Ru(PPh3)−CN−Fe(dppe)Cp][PF6]n (n=2, 3, 4) (L=dmptpy, 1[PF6]n; L=meoptpy, 2[PF6]n; L=t‐Buptpy, 3[PF6]n) (Cp=1,3‐cyclopentadiene, dppe=1,2‐bis(diphenylphosphino)ethane, PPh3=triphenylphosphine, dmptpy=4′‐(4‐dimethylaminophenyl)‐2,2′,6′,2′′‐terpyridine, meoptpy=4′‐(4‐methoxyphenyl)‐2,2′,6′,2′′‐terpyridine, t‐Buptpy=4′‐(4‐tertbutylphenyl)‐2,2′,6′,2′′‐terpyridine)). The investigations suggest that the cyanido‐stretching (νCN) vibration energy for the complexes is unsensitive to the electron‐donating ability change of the remote substituents of the cyanidometal bridging auxiliary ligand from tertbutyl, methoxy to dimethylamino group. However, the MMCT energies of the one‐ and two‐electron oxidation complexes are still sensitive to the remote substituents of the ligand on the bridging metal center, and decreases with the increase of the electron‐donating ability of the remote substituents from tertbutyl, methoxy to dimethylamino group. All one‐electron and two‐electron oxidation products belong to Class II mixed valence compounds according to the classification of Robin and Day. [ABSTRACT FROM AUTHOR]

Abstract Realizing dual charge transfer (CT) based on stable organic radicals in one system is a long‐sought goal, however, remains challenging. In this work, a stable mixed‐valence radical crystal is designed via a surfactant‐assisted method, namely TTF‐(TTF+•)2‐RC (where TTF = tetrathiafulvalene), containing dual CT interactions. The solubilization of surfactants enables successful co‐crystallization of mixed‐valence TTF molecules with different polarity in aqueous solutions. Short intermolecular distances between adjacent TTF moieties within TTF‐(TTF+•)2‐RC facilitate both inter‐valence CT (IVCT) between neutral TTF and TTF+•, and inter‐radical CT (IRCT) between two TTF+• in radical π‐dimer, which are confirmed by single‐crystal X‐ray diffraction, solid‐state absorption, electron spin resonance measurements, and DFT calculations. Moreover, TTF‐(TTF+•)2‐RC reveals an open‐shell singlet diradical ground state with the antiferromagnetic coupling of 2J = −657 cm−1 and an unprecedented temperature‐dependent magnetic property, manifesting the main monoradical characters of IVCT at 113–203 K while the spin‐spin interactions in radical dimers of IRCT are predominant at 263–353 K. Notably, dual CT characters endow TTF‐(TTF+•)2‐RC with strong light absorption over the full solar spectrum and outstanding stability. As a result, TTF‐(TTF+•)2‐RC exhibits significantly enhanced photothermal property, an increase of 46.6 °C within 180 s upon one‐sun illumination.

Two types of isostructural iron-cobalt/nickel-antimony-oxo tartrate cluster-based compounds, namely (H3O)(Me2NH2)[M(H2O)6]2[FeII2SbIII12(μ4-O)3(μ3-O)8(tta)6]·6H2O (M = Co (1); Ni (3)), H5/3[Co2.5FeII4/3FeIII3(H2O)13SbV1/3FeIII2/3(μ4-O)2(μ3-O)4SbIII6(μ3-O)2(tta)6]·2H2O (2) and H2[Ni2.25FeII1.5FeIII3(H2O)14SbV0.25FeIII0.75(μ4-O)2(μ3-O)4SbIII6(μ3-O)2(tta)6]·2H2O (4) (H4tta = tartaric acid) were synthesized via simple solvothermal reactions. All the clusters in the structures adopt sandwich configurations, that is, bilayer sandwich configuration in 1 and 3 and monolayer sandwich configuration in 2 and 4. Interestingly, the monolayer sandwiched compounds 2 and 4 represent rare examples of cluster-based compounds containing mixed-valence Sb(III, V), whose center of the intermediate layer is the co-occupied [FexSbV1−x]. This is different from that of previously reported sandwich-type antimony-oxo clusters in which the center position is either occupied by a transition metal ion or a Sb(V) alone. Thus, the discovery of title compounds 2 and 4 makes the evolution of center metal ion more complete, that is, from M, MxSbV1−x to SbV. All the title compounds were fully characterized, and the photocatalysis, proton conduction and magnetism of compounds 2 and 4 were studied.

One electron oxidation of the monometallic alkenylacetylide complexes [Ru{C≡CC(R)=CH2}(dppe)Cp*] (1) and [Ru{C≡CC(R)=CH2}Cl(dppe)2] (2) (R = Ph (a); R = 4-MeS-C6H4 (b)) generates in each case a dinuclear bis(allenylidene) complex [{Ru}2{μ-C=C=C(R)–CH2–H2C–(R)C=C=C}][PF6]2 ({Ru} = Ru(dppe)Cp* ([3a,b][PF6]2); {Ru} = RuCl(dppe)2 ([4a,b][PF6]2), containing an unsaturated ethane bridge between both allenylidene moieties. Deprotonation of this ethane bridge results in the formation of the previously reported octa-3,5-diene-1,7-diyndiyl-bridged bimetallic species [{Ru}2{μ-C≡CC(R)=CH–HC=(R)CC≡C}] ({Ru} = Ru(dppe)Cp* (5a,b); {Ru} = RuCl(dppe)2 (6a,b). The isolation of these complexes illustrates a general synthetic route to these conjugated bimetallic species from monomeric alkenylacetylide precursors. Electrochemical and spectroelectrochemical investigations evince the ready formation of the representative redox series [5a]n+, and TD-DFT calculations performed on optimised structures featuring the simplified {Ru(dmpe)Cp} coordination sphere [{Ru(dmpe)Cp}2{μ-C≡CC(Ph)=HC–CH(Ph)CC≡C}]n+ ([5a†]n+) (n = 0, 1, 2) reveal significant delocalisation of the unpaired charge in the formally mixed-valent species (n = 1), consistent with Class III assignment within the Robin–Day classification scheme.

Charge‐transfer (CT) engineering with inter‐/intramolecular CT interactions by simple compositions has emerged as a universal and efficient way to construct organic functional materials. Stable organic radicals with unique physicochemical properties that cannot be realized in closed‐shell molecules, have been widely demonstrated to be ideal building blocks to construct versatile organic CT materials. This concept article provides a brief overview of the advances in the design, structure and property of stable organic radicals‐based CT molecular functional materials, and the strategy for the generation of these materials is also highlighted. First, radicals are introduced as open‐shell donors or acceptors, with a focus on their importance and uniqueness in improving electrical, magnetic and optical properties of CT functional materials. Additionally, CT interactions in stable radical dimers and trimers are further discussed systematically. Finally, the challenges are summarized and perspectives for future development of stable organic radicals‐based CT functional materials are provided. [ABSTRACT FROM AUTHOR]

In this study, a hydrothermal process was utilized to grow mixed-valence CuFe 2 O 4 /Cu0 nanosheets on carbon fiber paper, forming a three-dimensional hierarchical electrode (CuFe 2 O 4 /Cu0@CFP). The ordered array structure, coupled with the porous bowl-like structure, enhances the exposure of more electrode active sites and facilitates analyte penetration, thus enhancing the electrode sensing performance. As a binder-free sensor, the CuFe 2 O 4 /Cu0@CFP sensor exhibited remarkable sensitivity in detecting Malachite Green (MG), Sunset Yellow (SY) and Tartrazine (TA) over wide concentration ranges: 0.1–300 μM for MG (R 2 = 0.994), 0.005–200 μM for SY (R 2 = 0.996), and 0.005–300 μM for TA (R 2 = 0.995) with low detection limits of 0.033 μM for MG, 0.0016 μM for SY, and 0.0016 μM for TA (S/N = 3), respectively. Additionally, the 3D CuFe 2 O 4 /Cu0@CFP sensor detected MG, SY, and TA in a mixed solution with satisfactory results. It also performs well in beverage, fruit juice powder, and jelly samples, with results matching those from HPLC. Graphic abstract [Display omitted] • Highly sensitive, selective and reliable voltammetric sensor was developed. • The sensor was made with 3D hierarchical CuFe 2 O 4 /Cu0 nanostructures@carbon fiber paper. • Simultaneous detection of Malachite Green, Sunset Yellow, and Tartrazine achieved. [ABSTRACT FROM AUTHOR]

Trinuclear Co(III)–Co(II)–Co(III) complexes, in which two {CoII(μ -O 2 CCH 3)(μ -OCH 3) 2 CoIII} units were linked by the edge-sharing manner, were synthesized and structurally characterized. Redox waves at the HS Co(II) center or LS Co(III) centers were all observed irreversibly. [Display omitted] • Linear-type cobalt trimers, in which the three octahedral cobalt centers were bridged by the CH 3 O− and CH 3 COO− ligands. • The electronic structure was found to be in the Co(III)–Co(II)–Co(III) (LS-HS-LS) state at room temperature. Two trinuclear cobalt complexes with the edge-sharing linear-type framework having benzylbis(2-pyridylmethyl)amine (bbpma), [{CoIII(bbpma)(μ -O 2 CCH 3)(μ -OCH 3) 2 } 2 CoII](X) 2 (X=ClO 4 ; [ 1 ](ClO 4) 2 , X =PF 6 ; [ 1 ](PF 6) 2), and one corresponding complex having ethylbis(2-pyridylmethyl)amine (ebpma), [{CoIII(ebpma)(μ -O 2 CCH 3)(μ -OCH 3) 2 } 2 CoII](PF 6) 2 ([ 2 ](PF 6) 2), were synthesized and the crystallographic and electronic structures were investigated. X-ray crystallography and magnetic measurements suggested that [ 1 ](PF 6) 2 and [ 2 ](PF 6) 2 were in the mixed-valent state and the mixed-spin state of Co(III)–Co(II)–Co(III) (LS-HS-LS), in which the electron spins were much localized on the central Co(II). [ABSTRACT FROM AUTHOR]

CoFeOX nanosheets were synthesized by a facile coprecipitation and calcination method. The effect of calcination temperature on the crystal texture, morphology and surface areas of CoFeOX were fully explored. CoFeOX sample calcined at 600 °C (CoFeOX‐600) showed superior catalytic performance for the reduction of CO2 under visible light. Compared with the pure Ru(bpy)32+‐sensitized CO2 reduction system, the CoFeOX‐added system achieved 19‐fold enhancement of CO production (45.7 μmol/h). The mixed valence state and nanosheet‐like structure of CoFeOX cocatalyst support its ultra‐high charge transfer and abundant CO2 active adsorption sites exposure, which promote the separation of photogenerated charges, and thus improve the photocatalytic CO2 reduction activity. Carbon source of CO from CO2 was verified by 13CO2 isotopic labelling experiment. Repeated activity experiments confirmed the good stability of CoFeOX in the CO2 photoreduction system. This work would provide prospective insights into developing novel cost‐effective, efficient, and durable non‐precious metal cocatalysts to improve the efficiency of photocatalytic reduction of CO2. [ABSTRACT FROM AUTHOR]

Single crystals of Na2Cu+[Cu2+3O](AsO4)2Cl (1) and Cu3[Cu3O]2(PO4)4Cl2 (2) were prepared by chemical vapor transport reactions. Both crystal structures are based upon the same [O2Cu6]8+ chains formed by corner-sharing (OCu4)6+ tetrahedra and interconnected by (TO4)3− (T = P, As) tetrahedra into porous {[OCu3](TO4)2Cl}3− frameworks. The channels within the frameworks are occupied by Na+, Cu+ and Cl− ions in the crystal structure of 1, whereas the channels in the structure of 2 contain edge-sharing CuO4Cl tetragonal pyramids. Both compounds are structurally related to the previously described synthetic Na2Cu+[Cu2+3O](PO4)2Cl and NaCu2+[Cu2+3O](PO4)2Cl. The compound 2 is structurally and chemically related to yaroshevskite, Cu3[Cu3O]2(VO4)4Cl2, a mineral discovered in volcanic fumaroles, but the two structure types are drastically different. The crystal chemical analysis of the title and related compounds allows to recognize a family of at least four compounds based upon {[OCu3](TO4)2Cl}3− frameworks with channels occupied by different chemical constituents. [ABSTRACT FROM AUTHOR]

A mixed-valence manganese selenite, Mn3O(SeO3)3, was successfully synthesized using a conventional hydrothermal method. The three-dimensional framework of this compound is composed of an MnO6 octahedra and an SeO3 trigonal pyramid. The magnetic topological arrangement of manganese ions shows a three-dimensional framework formed by the intersection of octa-kagomé spin sublattices and staircase-kagomé spin sublattices. Susceptibility, magnetization and heat capacity measurements confirm that Mn3O(SeO3)3 exhibits two successive long-range antiferromagnetic orderings with TN1~4.5 K and TN2~45 K and a field-induced spin–flop transition at a critical field of 4.5 T at low temperature. [ABSTRACT FROM AUTHOR]

Compounds and complexes with mixed‐valence electronic ground states, such as the Creutz–Taube ion, have proven to be excellent vehicles through which to study intramolecular electron‐transfer processes. In a recent contribution by Cadranel and co‐workers, time‐resolved pump‐probe spectroscopy reveals photo‐induced metal‐to‐bridge charge transfer within the homovalent analogue of the Creutz–Taube ion, [{(NH3)5Ru}(μ‐pz){Ru(NH3)5}]4+, giving rise to two closely lying excited states with mixed‐valence character, one with a shorter lifetime (τ=136 ps) and weakly‐coupled (Robin‐Day Class II) character, the other a longer‐lived (τ=2.8 ns) configurational isomer with more delocalized electronic structure. Electron transfer reactions from the longer‐lived species demonstrate analogies with the photo‐induced reactions of the photosynthetic special pair, suggesting this state as a reference system for excited state mixed‐valency, and a framework from which to explore photocatalytic reactions. [ABSTRACT FROM AUTHOR]

Mixed-valence compounds may provide molecular devices for an energy-efficient, low-power, general-purpose computing paradigm known as quantum-dot cellular automata (QCA). Multiple redox centers on mixed-valence molecules provide a system of coupled quantum dots. The configuration of mobile charge on a double-quantum-dot (DQD) molecule encodes a bit of classical information robust at room temperature. When arranged in non-homogeneous patterns (circuits) on a substrate, local Coulomb coupling between molecules enables information processing. While single-electron transistors and single-electron boxes could provide low-temperature solutions for reading the state of a ∼1 nm scale molecule, we propose a room-temperature read-out scheme. Here, DQD molecules are designed with slightly dissimilar quantum dots. Ab initio calculations show that the binary device states of an asymmetric molecule have distinct Raman spectra. Additionally, the dots are similar enough that mobile charge is not trapped on either dot, allowing device switching driven by the charge configuration of a neighbor molecule. A technique such as tip-enhanced Raman spectroscopy could be used to detect the state of a circuit comprised of several QCA molecules. [ABSTRACT FROM AUTHOR]

The development and applications of porous materials have been revolutionized over the past decades. To fine-tune their fascinating behaviors such as charge-transport, magnetic, and catalytic properties, one of the most effective strategies is incorporating mixed valency into the structures. This Concept provides recent progress on emerging crystalline porous materials, namely, metal-organic frameworks, metal-organic polyhedra, covalent organic frameworks, and hydrogen-bonded organic frameworks, where their mixed valency is either intrinsic or postsynthetically induced via an external stimulus. We further highlight the investigation of mixed valency and potential applications, which sheds light on the design and exploitation of mixed-valence crystalline porous materials., (© 2024 Wiley-VCH GmbH.)

The new complexes [1,3‐{Cp*(dppe)Fe−C≡C‐}2‐5‐(X)‐(C6H3)] (X=CH3, [m‐1 b]; X=C(O)OCH3, [m‐1 c]; X=C≡C−4−C6H4−C(O)OCH3, [m‐1 d]; X=C≡C−4−C6H4‐NO2, [m‐1 e]) were prepared by reaction of the iron chloride Cp*(dppe)FeCl (4) and the proligands 3 b–e obtained by a cross coupling reaction between the suitable aryl dibromides and trimethylsylilacethylene. After purification the complexes [m‐1 b–e] were isolated in yields ranging from 14 to 37 % and characterized by elemental analysis, high‐resolution, ESI‐mass spectra, multinuclear NMR, cyclic voltammetry, and IR spectroscopy. The complexes [m‐1 b], [m‐1 d], and [m‐1 e] were also characterized by XRD analyses on single crystals. The doubly oxidized complexes [m‐1 b–e](PF6)2 were prepared (in ca. 64–87 % yields) by treatment of a CH2Cl2 solution of the corresponding neutral complexes [m‐1 b–e] with two equiv. of [(C5H5)2Fe](PF6). The mixed‐valence complexes (MV) [m‐1 b–e](PF6) were obtained by comproportionation between one equiv. of [m‐1 b–e] and one equiv. of [m‐1 b–e](PF6)2. CV, IR and NIR data led to the conclusion that the MV [m‐1 b–e](PF6) complexes are weakly coupled Class II MV derivatives and the distribution of the charge between the alkynyl iron centers and the phenyl ring might be tuned by the X‐substituents in a limited extend. [ABSTRACT FROM AUTHOR]

In this article, we apply the two-mode vibronic model to the study of the dimeric molecular mixed-valence cell for quantum cellular automata. As such, we consider a multielectron mixed valence binuclear d² - d¹-type cluster, in which the double exchange, as well as the Heisenberg-Dirac-Van Vleck exchange interactions are operative, and also the local ("breathing") and intercenter vibrational modes are taken into account. The calculations of spin-vibronic energy spectra and the "cell-cell"-response function are carried out using quantum-mechanical two-mode vibronic approach based on the numerical solution of the dynamic vibronic problem. The obtained results demonstrate a possibility of combining the function of molecular QCA with that of spin switching in one electronic device and are expected to be useful from the point of view of the rational design of such multifunctional molecular electronic devices. [ABSTRACT FROM AUTHOR]

A mixed‐valent, one‐dimensional Cu(I/II) coordination polymer with the formula [CuII{CuI3(Hmpba)(mpba)2}DMF] ⋅ ∼3DMF was obtained with the bifunctional ligand 4‐(3,5‐dimethyl‐1H‐pyrazol‐4‐yl)benzoic acid (H2mpba) in N,N‐dimethylformamide (DMF) via solvothermal reaction. The compound exhibits a trinuclear {CuI3(Hmpba)(mpba)2}2− metallo‐linker with the softer Cu(I) linearly‐coordinated by the softer pyrazolate nitrogen donor atom. This metallo‐linker connects the harder Cu(II) ions through its harder carboxylate groups into a chain structure. Two Cu(II) ions form a paddlewheel unit and are, thus, surrounded by four carboxylate groups. Cu(II) is five‐coordinated with a terminal DMF ligand. Parallel chains are connected into supramolecular layers through the common R22(8) hydrogen‐bond motif of the singly‐deprotonated carboxyl groups of the Hmpba ligand. These layers are further organized by Cu(I)−Cu(I) interactions into a 3D supramolecular array. [ABSTRACT FROM AUTHOR]

A new π‐stacked compound, 1,8‐bis(2′,5′‐dimethoxy‐4′‐methyl‐[1,1′‐biphenyl]‐4‐yl)naphthalene (1) has been synthesized and characterized as a precursor molecule of monocationic mixed‐valence system (MVS). Cyclic and differential pulse voltammograms reveal that the ΔE°ox value between two sequential oxidation potentials is 163 mV. The three‐dimensional geometries of 1, 1•+, and 12+ were obtained via using density functional theory (DFT) calculations with a range‐separated hybrid functional and dispersion corrections (LC‐wPBE‐D3). Two dimethoxytoluene redox centers were aligned in parallel with van der Waals interplanar distances (3.50–3.70 Å). The electronic coupling in this MVS was evaluated by two different approaches: (1) Mulliken–Hush analysis of intervalence charge transfer (IVCT) band obtained from the spectroelectrochemical method, and (2) partial charge distribution analysis of quinonoidal distortion of D•+/D centers obtained from theoretical DFT calculations. The H12 were 2055 and 1903 cm−1 by (1) and (2), respectively. This work suggests that the pure through‐space electronic coupling can be large when two aromatic redox centers are properly aligned. [ABSTRACT FROM AUTHOR]

Electrochromic devices (ECDs) that allow the modulation of light transmission are very attractive in the research field of energy saving. Here all-in-one gel switchable ECDs based on mixed-valence electroactive compounds were developed. The use of the thienoviologen/ferrocene couple as cathode and anode, respectively, leads to a significant electrochromic band in the visible range (550–800 nm), with a color change from yellow to green, and to a lower band in the NIR region (1000–1700 nm), due to the presence of one electroactive-chromic species. Replacement of the electroactive ferrocene with a fluorene-diarylamine electroactive-chromic species, allows to extend and intensify the absorption in the NIR region, thus affording modulation of the solar radiation from 500 up to 2200 nm. High optical contrast, fast coloration and bleaching times and outstanding coloration efficiencies were measured for all observed absorption bands upon the application of small potential differences (1.4 V < ΔV < 2 V). [ABSTRACT FROM AUTHOR]

Four rutheniumethynyl‐triarylamine complexes 1–4 with different aryl bridge cores were prepared. The solid structures of complexes 2–4 were fully confirmed by X‐ray single‐crystal diffraction analysis. Two consecutive one‐electron oxidation processes of complexes 1–4 were attributed to the ruthenium and nitrogen centers, as revealed by cyclic voltammetry and square‐wave voltammogram. Results also showed decreasing potential difference ΔE of complexes 1, 3, and 4, with the largest value for 2. Upon chemical oxidation of complexes 1–4 by 1.0 eq oxidation reagents FcPF6 or AgSbF6, the mixed‐valence complexes, except for 2+, show characteristic broad NIR absorptions in the UV‐vis‐NIR spectroscopic experiments. NIR multiple absorptions were assigned to NAr2→RuCp*(dppe) intervalence charge transfer (IVCT) and metal‐to‐ligand charge transfer transitions by TDDFT calculations. Coupling parameter (Hab) from Hush theory revealed that increasing electronic communication in 1+, 3+, and 4+. Electron density distribution of the HOMO for neutral molecules (1, 3, and 4) and spin density distribution of the corresponding single‐oxidized states (1+, 3+, and 4+) increases progressively on the bridge as the size of the aromatic system increases, proving incremental contributions from bridge cores during oxidation. [ABSTRACT FROM AUTHOR]

It is promising and challenging to manipulate the electronic structures and functions of materials utilizing both metal‐to‐metal charge transfer (MMCT) and spin‐crossover (SCO) to tune the valence and spin states of metal ions. Herein, a metallocyanate building block is used to link with a FeII‐triazole moiety and generates a mixed‐valence complex {[(Tp4‐Me)FeIII(CN)3]9[FeII4(trz‐ph)6]}⋅[Ph3PMe]2⋅[(Tp4‐Me)FeIII(CN)3] (1; trz‐ph=4‐phenyl‐4H‐1,2,4‐triazole). Moreover, MMCT occurs between FeIII and one of the FeII sites after heat treatment, resulting in the generation of a new phase, {[(Tp4‐Me)FeII(CN)3][(Tp4‐Me)FeIII(CN)3]8 [FeIIIFeII3(trz‐ph)6]}⋅ [Ph3PMe]2⋅[(Tp4‐Me)FeIII(CN)3] (1 a). Structural and magnetic studies reveal that MMCT can tune the two‐step SCO behavior of 1 into one‐step SCO behavior of 1 a. Our work demonstrates that the integration of MMCT and SCO can provide a new alternative for manipulating functional spin‐transition materials with accessible multi‐electronic states. [ABSTRACT FROM AUTHOR]

The effect of the double exchange in a square-planar mixed-valence dn+1 - dn+1 - dn - dn-type tetramers comprising two excess electrons delocalized over four spin cores is discussed. The detailed analysis of a relatively simple d2 - d2 - d1 - d1-type tetramer shows that in system with the delocalized electronic pair the double exchange is able to produce antiferromagnetic spin alignment. This is drastically different from the customary ferromagnetic effect of the double exchange which is well established for mixed-valence dimers and tetramers with one excess electron or hole. That is why the question "Can double exchange cause antiferromagnetic spin alignment?" became the title of this article. As an answer to this question the qualitative and quantitative study revealed that due to antiparallel directions of spins of the two mobile electrons which give competitive contributions to the overall polarization of spin cores, the system entirely becomes antiferromagnetic. It has been also shown that depending on the relative strength of the second-order double exchange and Heisenberg-Dirac-Van Vleck exchange the system has either the ground localized spin-triplet or the ground delocalized spin-singlet. [ABSTRACT FROM AUTHOR]

The bis(ironvinylidene) complex [1,4-{Cp*(dppe)Fe= C=CH}2-2,5-(C=CH)2-C6H2](PF6)2 ([2-2H](PF6)2) was prepared from 1,2,4,5-tetraethynylbenzene and two equiv. of Cp*(dppe)FeCl in 87% yield. The reaction is very selective and [2-2H](PF6)2 is the unique organoiron species to be formed. Deprotonation of [2-2H](PF6)2 provided the target complex 2 (66% yield) and subsequent oxidation gave the monocationic and dicationic complexes 2(PF6) and 2(PF6)2. The new complexes were characterized by ESI-mass spectrometry, IR, multinuclear NMR, ESR and Mössbauer spectroscopy, and XRD analyses on single crystals for [2-2H](PF6)2 and 2(PF6)2. The magnetic properties of 2(PF6)2 were investigated by VT ¹H NMR. The data were analyzed with the support of quantum chemistry calculations. The terminal ethynyl groups on the aromatic ring of the bridge modify the population of the bridge-oxidized state, weaken the electronic communication (Hab 601 cm-1) and strengthen magnetic coupling interactions (J = -530 cm-1) compared to the unsubstituted species (Hab = 1700 cm-1 and J = -340 cm-1, respectively). [ABSTRACT FROM AUTHOR]

The unprecedented tetrairon dication [{Cp*(dppe)FeC≡C‐}4‐μ‐(1,2,4,5‐C6H2)](PF6)2 (1) was obtained through a sequence of three reactions from 1,2,4,5‐tetraethynylbenzene, Cp*(dppe)FeCl (Cp*=C5Me5, dppe=1,2‐bis(diphenylphosphino)‐ethane), KOtBu, and ferrocenium hexafluorophosphate. The cyclic voltammogram of the target molecule, isolated in 77 % yield, exhibits four well separated and reversible redox events showing that 1 is thermodynamically stable with respect to disproportionation (Kc>106). The tetranuclear dication 1 was characterized by XRD on single crystal, IR and NMR spectroscopies and Mössbauer spectrometry. The experimental data show that 1 behaves as a class II mixed‐valence complex with the positive charges preferentially disposed on antipodal positions. This new molecule can be regarded as a potential molecular prototype of quantum dot cellular automata. [ABSTRACT FROM AUTHOR]

Mixed valency is a well-known phenomenon in which charge distributions can change via intervalence charge transfer. In addition, there are many other ubiquitous phenomena for charges such as proton transfer, zwitterionization, charge separation, and some supramolecular interactions. However, a basic understanding of the interface between mixed valency and other charge-involved phenomena remains poor. Recent progress is described in creating mixed-valence subspecies by introducing stimuli-responsiveness to conventional mixed-valence frameworks and interplay between mobile charges and charges introduced via light and ions. [ABSTRACT FROM AUTHOR]

Near-infrared electrochromic materials have garnered great attention due to their potential applications in optical data storage and military camouflage. Herein, a networked metal-organic coordination polymer bearing multi-redox centra (Fe-MCP) was successfully prepared by coordination interaction of Fe ions with D-A-D-structure ligands through the liquid-liquid interface self-assembly strategy. The resultant uniform film exhibits improved NIR electrochromic attributed to the construction of mixed-valence system. Furthermore, a sandwich-structured electrochromic device was fabricated by combining Fe-MCP electrochromic layer, a gel composed of LiClO 4 , PMMA, and PC as the electrolyte layer, and anodically coloring PB as an ion storage layer. The resultant device illustrated an optical contrast of 31.4 % at 800 nm and 34.2 % at 1000 nm, a response speed of 4.0 s/8.3 s at 800 nm and 7.6 s/2.7 s at 1000 nm, and good cycling durability. The design principles proposed in this study provide a new insight for the preparation of high-performance NIR electrochromic materials. • A novel networked metal-organic coordination polymer with mixed-valence system was synthesized. • Assembled device shows electrochromic performance in both visible and near-infrared regions. • Large optical contrast and good cycling durability were revealed due to the mixed-valence system. [ABSTRACT FROM AUTHOR]

In this article, we apply the two-mode vibronic model to the study of the dimeric molecular mixed-valence cell for quantum cellular automata. As such, we consider a multielectron mixed valence binuclear d2−d1–type cluster, in which the double exchange, as well as the Heisenberg-Dirac-Van Vleck exchange interactions are operative, and also the local (“breathing”) and intercenter vibrational modes are taken into account. The calculations of spin-vibronic energy spectra and the “cell-cell”-response function are carried out using quantum-mechanical two-mode vibronic approach based on the numerical solution of the dynamic vibronic problem. The obtained results demonstrate a possibility of combining the function of molecular QCA with that of spin switching in one electronic device and are expected to be useful from the point of view of the rational design of such multifunctional molecular electronic devices.

A metal-formate framework with novel topology of (49·66) 2 (412·63), [DMA] 2 [FeIIIFe 2 II(HCOO) 9 ] (DMA = (CH 3) 2 NH 2 +), has been synthesized via solvothermal method, which exhibits long-range weak ferromagnetic ordering below 33 K. The Mössbauer spectra demonstrated the composite of the complex is a mixture valence of FeIII and FeII. A metal-formate framework of [DMA] 2 [FeIIIFe 2 II(HCOO) 9 ] (DMA = (CH 3) 2 NH 2 +) with novel topology of (49·66) 2 (412·63) was prepared. The Mössbauer spectra demonstrated the composite of the complex has a mixture valence of FeIII and FeII. Unlabelled Image • The occurrence of rare topology of (4966) 2 (41263). • The Mössbauer spectra demonstrated a mixture valence of FeIII and FeII. • The observation of long-range ferromagnetic ordering below 33 K. [ABSTRACT FROM AUTHOR]

Abstract A hollow graphitized carbon nanosphere/mixed-valence manganese oxide composite (HMO) was successfully synthesized via a SiO 2 template and impregnation-reduction method. The chemical valence and content of manganese species were controlled by the reaction time of impregnation-reduction process. The HMO composite obtained by impregnation-reduction for 6 h (HMO-6) shows a large specific capacitance (292.5 F g−1 at 0.5 A g−1), excellent cycling stability (96.8% after 5000 cycles at 1 A g−1) and rate performance (155.3 F g−1 at 10 A g−1). The interior graphitized carbon shell, hollow porous structure, higher surface area, and appropriate percentage of Mn2+, Mn3+ and Mn4+ species are responsible for the superior electrochemical performance. The asymmetric supercapacitor composed of HMO-6 and hollow graphitized carbon nanosphere (HCS) also shows a superior electrochemical performance in all-solid-state asymmetric supercapacitor. The design and synthesis strategy of electrode materials offers a promising approach to develop high-performance manganese oxide supercapacitors. Graphical abstract Unlabelled Image Highlights • A new strategy for designing hollow graphitized carbon nanosphere/mixed-valence manganese oxide composites • The electrodes exhibited high specific capacitance, excellent cycle stability and rate capability. • The aqueous and all-solid-state asymmetric supercapacitors deliver high energy and power density. • This multistage design and valence modulation strategy could be extended to other electrode materials. [ABSTRACT FROM AUTHOR]

Abstract A new one-dimensional coordination polymer, [Cu II (L) 2 ][Cu I (bpy)] 2 ·4H 2 O (BUC-20) (H 2 L = cis -1,3-dibenzyl-2-imidazolidone-4,5-dicarboxylic acid, bpy = 4,4-bipyridine), was synthesized solvothermal condition. The crystal structure of BUC-20 was analyzed, and its properties like band energy, water stability, and photocurrent were clarified. BUC-20 exhibited outstanding photocatalytic Cr(VI) performance upon the UV light irradiation under acid condition, which was superior to those of existing photocatalysts. The photocatalytic performance was not influenced by the presence of inorganic ions, which was affirmed by the introduction real surface water to prepare simulated wastewater. BUC-20 exhibited good water stability, and could be used several runs without significant efficiency decrease. Graphical abstract Image 1 Highlights • BUC-20 is a water stable 1D coordination polymer containing mixed-valence CuI/CuII. • BUC-20 displays excellent photocatalytic Cr(VI) reduction under UV light irradiation. • The photocatalytic activity isn't effected by co-existing ions in real surface water. • BUC-20 can be used as efficient photocatalyst for several runs. [ABSTRACT FROM AUTHOR]

Abstract The valence states and local structure around Mn atoms in mixed-valence Mn 2 BO 4 have been studied by temperature dependent X-ray powder diffraction (XRPD), X-ray photoelectron (XPS) and Mn K -edge X-ray absorption (XAFS) spectroscopies measurements. X-ray absorption near-edge structure (XANES) and XPS have been used to measure the average oxidation state of Mn in bulk and near-surface of the material. The edge position, peak shapes and pre-edge features of Mn K -edge XANES spectra have been discussed. The pronounced temperature dependence of the Debye-Waller (DW) factor corresponding to the Mn O coordination shell has been found from the extended x-ray absorption fine structure (EXAFS) analysis and has been associated with variations in the local distortions in MnO 6 octahedra and emergence of short-range magnetic correlations at low temperatures. The XRPD measurements have been carried out at 298, 523 and 773 K. The monoclinic symmetry (P 2 1 / n) was found to persist up to highest temperature measured. The BVS calculations have revealed large valence difference between two manganese sites that strongly supports the presence of charge ordering up to high temperatures. Highlights •The monoclinic symmetry was found to persist up to 973 K. •The large bond-valence difference between Mn1 and Mn2 sites suggests the presence of the charge ordering up to highest temperature measured. •The DW factor is progressively reduced below 100 K and goes through a minimum at the T N. •The average manganese oxidation state in bulk was found to be Mn(2.55±0.08)+. [ABSTRACT FROM AUTHOR]

Dimeric mixed‐valence vanadium (IV/V) glycolates and lactates with N‐heterocycle ligands, [V2O3(phen)3(glyc)]Cl·7H2O (1), [V2O3(phen)3(S‐lact)]Cl·5.5H2O (2), (NH4)2[V2O3(bpy)2(glyc)2]Cl·4H2O (3), (NH4)[V2O3(bpy)2(S‐lact)2]·7H2O (4) and (NH4)2[V2O3(bpy)2(R,S‐lact)2]Cl·H2O (5), have been isolated in a wide pH range from weak acidic to alkaline solutions (H2glyc = glycolic acid, H2lact = lactic acid, phen = 1,10‐phenanthroline, bpy = 2,2′‐bipyridine). The glycolates and lactates in 1 and 2 chelate to VV whereas in 3–5 chelate to VIV and VV with α‐alkoxy and α‐carboxy groups. These complexes feature interesting localized O=VIV–O–VV=O bridging structures, which are supported by structural analyses, bond valance calculations, UV/Vis, EPR experiments and exhibit different electrochemical behaviors. These complexes were further used for the selective oxidation of thioanisole to methyl phenyl sulfoxide. Two kinds of dimeric mixed‐valence vanadium (IV/V) glycolates and lactates with localized O=VIV–O–VV=O bridging structures exhibit distinct spectroscopy and redox properties, which are used in the catalytic oxidation of thioanisole. [ABSTRACT FROM AUTHOR]

Abstract With an aim to obtain a new supramolecular compound based on Keggin-type polyoxometalates with mixed-ligand: [Cu(I)(phen) 2 ] 2 {[Cu(II)] 2 (phen) 4 PTA}[H 3 PMoV 4 MoVI 8 O 40 ] (phen = 1,10-phenanthroline, PTA = terephthalic acid) has been synthesized under hydrothermal conditions and structurally characterized by elemental analyses, IR, X-ray single crystal diffraction, TG analyses and XPS. In the title compound, the Keggin-type phosphomolybates anions, butterfly-shaped [Cu(I)(phen) 2 ]+ subunits and dumbbell-shaped {[Cu(II)] 2 (phen) 4 PTA}2+ subunits are alternately connected to form chiral helical chains via hydrogen bonds along b axis, and the adjacent chiral helical chains are connected in the way of sharing butterfly-shaped [Cu(I)(phen) 2 ]+ subunits and dumbbell-shaped {[Cu(II)] 2 (phen) 4 PTA}2+ subunits to form 3D supramolecular reticular framework. As expected, the title compound with mixed-ligands (phen and PTA) has been successfully synthesized, inconceivably, the title compound also contains mixed-valence Cu (Cu(I) in butterfly-shaped [Cu(I)(phen) 2 ]+ subunits; Cu(II) in dumbbell-shaped {[Cu(II)] 2 (phen) 4 PTA}2+ subunits). The preliminary analyses show that mixed-valence Cu(I/II) may be due to the reduction of Cu(II) (from CuCl 2) to Cu(I) (in butterfly-shaped [Cu(I)(phen) 2 ]+ subunits) by N-containing compound. The successful results of this work provide a new idea that supramolecular materials with attractive structures and novel properties, which could be designed and synthesized by introducing of mixed-ligands into the supramolecular materials. Additionally, the electrocatalytic property of the title compound to H 2 O 2 has been studied. Graphical abstract Unlabelled Image Highlights • Compound based on Keggin POMs with mixed-ligand and Cu(I/II) was prepared. • The compound contains the right- and left-hand helical chains. • The compound exhibits good electrocatalytic activity towards H 2 O 2 reduction [ABSTRACT FROM AUTHOR]

[Display omitted] • Two mixed-valence manganese based compounds A 2 MnⅡMn 2 III(SeO 3) 6 (A = Sr and Ba) are obtained by hydrothermal method. • These compounds exhibit Mn3+ ions located in a distorted honeycomb motif centred by the Mn2+ ions. • These compounds show a short-range and a long-range antiferromagnetic order at low temperature. • These compounds show a metamagnetic transition under applied fields. A 2 MnⅡMn 2 III(SeO 3) 6 (A = Sr and Ba) are found to have a monoclinic space group P 2 1 / c , where Mn3+ ions form a distorted honeycomb lattice centred by the Mn2+ ions. The samples of two isostructural compounds were synthesized using a conventional hydrothermal method and characterized by many methods including EDS, XRD, FT-IR, UV–vis diffuse reflectance spectra and thermal analysis. Magnetic measurements confirm that two compounds display a similar magnetic behavior with a short-range and a long-range antiferromagnetic order at low temperature, while the metamagnetic transition can be observed under applied magnetic field. In addition, the spin-frustration effects of two compounds are also investigated. [ABSTRACT FROM AUTHOR]

• Fe(II)/Fe(III) formate framework was presented for Li-storage anode. • The framework delivered a reversible capacity of ≈920 mAh/g at 50 mA g−1. • 683 mAh/g at 0.5 A/g and 500 cycles with 73% retention were also achieved. • Reversible conversion accompanying self-nano-crystallization was disclosed. Metal organic frameworks (MOFs) with metal active sites of mixed-valence are still less studied for Li-storage, especially for the anode. We present the Li-storage performance of a formate framework with both Fe(II) and Fe(III) as active sites. It delivered an impressive reversible capacity of ≈920 mAh/g at 50 mA g−1, good rate performance of 683 mAh/g at 500 mA g−1, and long-term cycling stability of 500 cycles with 73% capacity retention. Reversible structure conversion accompanying self-nano-crystallization at certain crystal directions accounts for the good cycling stability and progressively improved rate performance. [ABSTRACT FROM AUTHOR]

Electrochromic devices (ECDs) that allow the modulation of light transmission are very attractive in the research field of energy saving. Here all-in-one gel switchable ECDs based on mixed-valence electroactive compounds were developed. The use of the thienoviologen/ferrocene couple as cathode and anode, respectively, leads to a significant electrochromic band in the visible range (550–800 nm), with a color change from yellow to green, and to a lower band in the NIR region (1000–1700 nm), due to the presence of one electroactive-chromic species. Replacement of the electroactive ferrocene with a fluorene-diarylamine electroactive-chromic species, allows to extend and intensify the absorption in the NIR region, thus affording modulation of the solar radiation from 500 up to 2200 nm. High optical contrast, fast coloration and bleaching times and outstanding coloration efficiencies were measured for all observed absorption bands upon the application of small potential differences (1.4 V < DV < 2 V).

The effect of the double exchange in a square-planar mixed-valence dn+1−dn+1−dn−dn–type tetramers comprising two excess electrons delocalized over four spin cores is discussed. The detailed analysis of a relatively simple d2−d2−d1−d1–type tetramer shows that in system with the delocalized electronic pair the double exchange is able to produce antiferromagnetic spin alignment. This is drastically different from the customary ferromagnetic effect of the double exchange which is well established for mixed-valence dimers and tetramers with one excess electron or hole. That is why the question “Can double exchange cause antiferromagnetic spin alignment?” became the title of this article. As an answer to this question the qualitative and quantitative study revealed that due to antiparallel directions of spins of the two mobile electrons which give competitive contributions to the overall polarization of spin cores, the system entirely becomes antiferromagnetic. It has been also shown that depending on the relative strength of the second-order double exchange and Heisenberg–Dirac–Van Vleck exchange the system has either the ground localized spin-triplet or the ground delocalized spin-singlet.

A new mixed-valence Cu(I)–Cu(II) 1D coordination polymer, [CuI4CuIIBr4(Cy2dtc)2]n, with an infinite chain structure is synthesized by the reaction of Cu(Cy2dtc)2 (Cy2dtc− = dicyclohexyl dithiocarbamate, C13H22NS2) with CuBr·S(CH3)2. The as-synthesized polymer consists of mononuclear copper(II) units of CuII(Cy2dtc)2 and tetranuclear copper(I) cluster units, CuI4Br4. In the cluster unit, all the CuI ions have distorted trigonal pyramidal coordination geometries, and the CuI–CuI or CuI–CuII distances between the nearest copper ions are shorter than the sum of van der Waals radii for Cu–Cu.

Reaction of nickel and zinc triflates with the tridentate leucoverdazyl 1-isopropyl-3,5-di (2'-pyridyl)-6-oxo-2H-tetrazine (dipyvdH) and triethylamine resulted in the neutral coordination compounds M(dipyvd) 2 (M = Ni,Zn). In acetonitrile, both compounds undergo two one electron oxidation processes, Zn (dipyvd) 2  at -0.28 V and -0.12 V and Ni(dipyvd) 2  at -0.32 V and -0.15 V vs ferrocene/ferricenium. Oxidations are ligand based resulting in an intermediate mixed valence species and a cationic bis(verdazyl) compound respectively. Oxidation of the ligand changes a localized, antiaromatic, non-planar 8π electron anion to a planar, delocalized 7π electron radical. The change in ligand structure results in an increase in the octahedral ligand field splitting from 10,500 cm -1 to ∼13,000 cm -1 , suggesting an increase in the pi acceptor character of the ligand. In the mixed valence species, spectroscopic data suggests minimal interaction between ligands mediated by the metal center; i.e., these are class I-II systems in the Robin-Day classification., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Fleming, Vu, Brook, Agrestini, Pellegrin and DaRos.)

Two polynuclear, mixed-valence, sandwich dodecanuclear manganese clusters [MnII4MnIII4MnII4(μ4-O)2(μ3-O2CH)2(thme)4(MeCO2)10(H2O)4]·4H2O (1) and [MnII4MnIII4MnII4(μ4-O)2(μ3-O)2(thmp)4(MeCO2)10(H2O)4]·10H2O (2) are reported by the reaction of 1,1,1-tris(hydroxymethyl)ethane (H3thme) or 1,1,1-tris(hydroxymethyl)propane (H3thmp) with manganese(II) salts in methanol under reflux conditions. 1 and 2 were characterized by single-crystal X-ray diffraction, PXRD, cyclic voltammetry (CV), and variable temperature magnetic studies. 1 and 2 crystallize in the monoclinic (P21/n) and triclinic (P-1) systems, respectively, and each structure consists of a dodecanuclear mixed-valent sandwich core. Magnetic data confirmed that both complexes show dominant antiferromagnetic interactions between metal centers. The fascinating features of the non-covalent supramolecular contacts have been explored. The interplay of O⋯H interactions (i.e. O-H⋯O and C-H⋯O contacts) gives rise to the consolidation of discrete units of 1 and 2 into supramolecular architecture. Catecholase activity data show that the present clusters catalyze the oxidation of 3,5-DTBC to 3,5-DTBQ with efficient Kcat values. [ABSTRACT FROM AUTHOR]

Abstract: Reactions of the organotin selenide chloride clusters [(R1SnIV)3Se4Cl] (A, R1=CMe2CH2C(O)Me) or [(R1SnIV)4Se6] (B) with [Cu(PPh3)3−xClx] yield cluster compounds with different inorganic, mixed‐valence core structures: [Cu4SnIISnIV6Se12], [Cu2SnII2SnIV4Se8Cl2], [Cu2SnIISnIV4Se8], [Cu2SnII2SnIV2Se4Cl4], and [Cu2SnIV2Se4]. Five of the compounds, namely [(CuPPh3)2{(R1SnIV)2Se4}] (1), [(CuPPh3)2SnII{(R2SnIV)2Se4}2] (2), [(CuPPh3)2(SnIICl)2{(RSnIV)2Se4}2] (3) [(CuPPh3)2(SnIICu2){(R1SnIV)2Se4}3] (4), and [Cu(CuPPh3)(SnIICu2){(R1SnIV)2Se4}3] (5) are structurally closely related. They are based on [(CuPPh3)2{(RSnIV)2Se4}n] aggregates comprising [(RSnIV)2Se4] and [CuPPh3] building units, which are linked by further metal atoms. A sixth compound, [(CuPPh3)2(SnIICl)2{(R1SnIVCl)Se2}2] (6), differs from the others by containing [(RSnIVCl)Se2] units instead, which affects the absorption properties. The compounds were analyzed by single‐crystal X‐ray diffraction, NMR and 119Sn Mössbauer spectroscopy, DFT calculations as well as optical absorption experiments. [ABSTRACT FROM AUTHOR]

A series of germinal -diethynylethene ( gem -DEE) bridged diferrocenyl compounds, including 1,1-[bis(ferrocenylethynyl)methylene]cyclohexane ( 1 ), 1,1-[bis(ferrocenylethynyl)methylene]tetrahydro-2 H -pyran ( 2 ), and 1,1-[bis(ferrocenylethynyl)methylene]tetrahydro-2 H -thiopyran ( 3 ) were synthesized and characterized. The Fe ⋯ Fe distance between the two ferrocenyl termini reaches up to ∼9 Å for compounds 2 and 3 . The electrochemical measurements demonstrate moderate electronic coupling between the gem -DEE-bridged ferrocenyl (Fc) termini in this cross-conjugated system. UV–vis–NIR spectroscopy studies suggest that the monocation species of these compounds belong to class II mixed-valence systems in Robin–Day classification. DFT calculations further reveal electronic structures of these cross-conjugated diferrocenyl compounds. [ABSTRACT FROM AUTHOR]